Multi-spring leg apex-type snap action switch



1968 R. w. FRASER ETAL. 3,410,973

MULTI-SPRING LEG APEX-TYPE SNAP ACTION SWITCH Filed Dc. 6, 1966 5Sheets-Sheet 1 I6 30 1a 70 22 24 I l! 2 FIG! 58 34 66 I 12 Q 32 2 4 2270 20 5o Q 42 F162 5a I2 54.; i 4o 0 34 38 INVENTOR 43 ROBERT W. FRASERBY, WILLIAM H. FLANAGAN ATTORNEY Nov. 12, 1968 R, w. FRASER ETAL3,410,973

MULTI-SPRING LEG APEX-TYPE SNAP ACTION SWITCH F I G. 3

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f 4 38 3 INVENTORS ROBERT W.FRASER w WILLIAM H. FLANAGAN BY, .6 43 4 3s3. 70.

ATTORNEY Nov. 12, 1968 R. w. FRASER ETAL. 3,410,973

MULTI-SPRING LEG APEX-TYPE SNAP ACTION SWITCH Filed Dec. 6, 1966 sSheets-Shed 5 67 w L 1 FIG.4

INVENTORS ATTORNEY United States Patent Office 3,410,973 Patented Nov.12, 1968 3,410,973 MULTISPRING LEG APEX-TYPE SNAP ACTION SWITCH RobertW. Fraser and William H. Flanagan, Stamford, Conn., assignors to Nexus,Inc., Stamford, Conn., a corporation of Connecticut Filed Dec. 6, 1966,Ser. No. 599,610 1 Claim. (Cl. 200-77) ABSTRACT OF THE DISCLOSURE Amulti-legged apex type snap action electrical switch having an aperturedcontact moveable axially in response to manual operation of a plungerinto engagement with fixed contacts.

This invention relates generally to electrical devices and moreparticularly to improved snap-action plunger switches of the type usedfor closing and opening of electrical circuits.

Snap-action switches as they are generally known have been utilized inaircraft communications and ordnance equipment and wherever constantpressure on the actuator is required to close or open an electricalcircuit. Since the majority of these switches are of the miniature type,extreme care has to be taken with their development to insulate theconductors from the non-conductors by a dielectric. With existingswitches it has been determined that after a period of use vapormetallic deposits build up on the non-conductive surfaces as a result ofarcing causing the switch to short and become inoperative. Basicallythis is caused by the miniaturization of the switch itself by reducingthe over-surface distance between the stationary and moveable contacts.Since air is an etficient dielectric, this invention represents a newand novel improvement wherein the distance between the conductors at themake and break points and the nonconductors is increased.

Therefore, it is an object of this invention to provide an improved andsimple, novel and inexpensive snap-action switch having a longerelectrical life than existing switches.

It is another object of this invention to provide a switch in which theactuator is self-aligning and has short radial movement.

It is still another object of this invention to provide an improved typeof a plunger switch wherein the camrning member is freely rotatable andhas a plurality of segmental spring members, thus providing increasedpressure in moving the moveable contact into engagement with the fixedcontacts.

It is a further object of this invention to provide an improvedsnap-action plunger switch wherein the moveable contact is of slightmass and resistant to inadvertent closing during moments of vibrationalstress.

It is still a further object of this invention to provide an improvedminiature switch wherein the conducting contacts are isolated from thenon-conducting elements by an air dielectric reducing the metallic vapordeposits on the non-conducting elements.

Other objects of this invention will in part be obvious and will in partappear hereinafter.

Broadly stated the feature of this invention is to provide a snap-actionplunger type switch whereby the oversurface difference between thecontact points and the insulator is increased so that any metallic vaporbuild up is remote from the conductors so as to maintain a good andefiective dielectric therebetween.

To the accomplishment of this and the foregoing related ends, thepresent invention then consists of the means hereinafter fully describedand particularly pointed out in the claims, the annexed drawings and thefollowing description setting forth in detail certain means in thecarrying out of the invention, such disclosed means illustrating,however, but one of the various ways in which the principle of theinvention may be employed.

In the drawings:

FIG. 1 is a cut-away view of the switch partly in section illustratingthe operational components.

FIG. 2 is a view in section taken on line 2-2 of FIG. 1.

FIG. 3 is an exploded view of the switch.

FIGURE 4 is a top plan view showing the apertured floating contact andthe surrounding parts.

FIG. 5 is a view in section of a modified form of the switch.

Referring to the drawings there is shown in FIGS. 1-3 a switch 10comprising an outer housing 12 having an annular shoulder 14 formedthereon and a male threaded portion 16 adapted to co-operate with apanel or the like (not shown) and to allow the shoulder 14 to bepositioned in abutting relationship therewith.

Within the housing 12 there is located a tubular hollow first insulator18 formed of a dielectric having an external configuration with anannular flange 20 adapted to con- -form to the interior and cooperatingwith an interior shoulder 22 of the housing 12. The insulator 18 has apair of annular shoulders 24 and 26 axially spaced from each other andformed on the interior wall 30 thereof for purposes to be more fullydescribed hereinafter.

A second insulator 32 fits within the first insulator 18 and abuts witha shoulder 34 against the distal end 36 of the first insulator. Thesecond insulator 32 is formed of a dielectric such as diallyl phthalateor allyl resins and has molded integral therewith two or more stationarycontact members 38. The first set of stationary contact members 38 haveangular bends 40 so as to define surface areas 42 which are laterallyspaced from each other but in the same plane. A second set of contactmembers 43 are disposed in the second insulator v32 in coaxialrelationship to said first set of stationary contacts which are normallyclosed. A longitudinal bore 44 is provided in the second insulator andis open to one surface 46 thereof to receive and retain a coiled spring48. A return pin 50 extends downwardly from the tubularly hollow firstinsulator 18 and has a shank 52 of a diameter less than the internaldiameter of the coil spring 48. An annular shoulder 54 is formed on thereturn pin 50 at a point spaced from the end 56 of the shank 52 and hasan external diameter greater than the diameter of the spring 48 tomaintain the shank in a fixed position relative to the spring. The mainbody of the return pin extends upwardly as shown in FIG. 3 through anapertured floating contact 58. The upper end 60 of the return pin 50 istapered to fit within a mating recess 62 of an actuator 64.

The floating contact 58 as shown in FIG. 4 consists of a rectangularconductive plate having a central aperture 66 and laterally extendingtongue members 67 adapted to travel in channels 69 formed in the wallsof the first insulator. The contact is formed of a light material so ashave little mass and be unaffected by shock or vibration. The upwardtravel of the floating contact 58 is limited by the annular shoulder 24formed in the wall of the first insulator or by stationary contacts 43.The lower travel of the floating contact is limited by the surface areas42 of the stationary contacts 38.

The actuator 64 comprises an elongated hollow tubular member having aclosed end portion 68. Extending longitudinally therefrom are foursegmental spring members 70 separated from one another by gaps 72. Eachof the segmental spring members is tapered in opposite directions toform oblique surfaces 74 around the center line of the actuator 64. Theoblique surfaces terminate at an annular apex 76 from which the members70 converge toward the center line of the actuator 74 to form guidesurfaces 78. The segmental spring members 70 when fully compressed havea diameter at the apex less than the internal diameter of the aperture66 of the floating contact 58 for a purpose to be set forth more fullyhereinafter. The actuator 64 is rotatable to provide a uniform bearingsurface and smoother action.

Completing the switch assembly is a plunger 80 comprising a closed capportion 82 having a central bore 84 for receiving the closed end 68 ofthe actuator 64. An external flange 86 causes the plunger 80 to beretained in assembly by abutting against a shoulder 88 in the housing14.

In operation the plunger 80 upon being depressed forces the actuatordownward overcoming the pressure exerted on the return pin 50 by thecoil spring 48. The clearance within the segmental members 70 byreceiving the return pin 50 allows the leading surfaces 78 to alignthemselves with the aperture 66 in the floating contact 58. The leadingsurfaces 78 upon entering the aperture 66 cause the segmental springmembers to constrict inward-1y toward the center line of the actuator,thereby allowing the leading surfaces 78 to enter the aperture until theapex 76 traverses the aperture and causes the floating contact member tosnap upwardly, thereby breaking the electric connection between the twosurface areas 42 of the stationary contact members 38 while forcing themoveable contact 58 into electrical contact with the second set ofstationary contact members 43. The upward travel of the floating contactmember is limited either by the annular shoulder 24 formed in theinterior wall 30 of the first insulator 18 or by the stationary contacts43. Upon release of the pressure on the plunger 80', the coiled spring48 forces the return pin 50 carrying the actuator 64 upward so that theoblique surfaces 74 are compressed by the aperture 66 until the apex hasa diameter less than the diameter of the aperture when the floatingcontact 58 snaps toward and into contact with stationary contacts 38.

As shown in FIGURE 5, a modified form of the invention may be providedwherein a single throw switch operates on the same principle.

The switch consists of an outer housing 12a containing a first insulator18a having an annular shoulder 14a at one end and a male threadedportion 16a on the housing adjacent the shoulder. The first insulator18a also has an annular flange 20a cooperating with a shoulder 22a ofthe housing 12a. The insulator 18a has annular shoulders 24a and 26aaxially spaced from each other and "formed on the interior wall 30a forpurposes to be more fully described hereinafter.

A second insulator 32a fits within the first insulator 18a and has ashoulder 340 on the exterior surface thereof which abuts against thedistal end 36a of the first insulator. The second insulator is for-medof a dielectric such as diallyl phthalate Or one of the allyl resins andhas molded integral therewith two stationary contact members 38a. Thestationary contact members 38a have angular bends 40a so as to providesurface areas 42a which are laterally spaced from each other but in thesame plane.

A floating contact member 44a positioned within the tubular hollow firstinsulator 18a has a central aperture 46a and laterally extending tonguemembers 48a adapted to travel in channels formed in the walls of thefirst insulator to prevent rotation. The upward travel of the floatingcontact member 44a is limited by the annular shoulder 26a or by the bentends of stationary contacts 43a. The downward travel of the floatingcontact is limited by the surface areas 42a of the bent ends of stationary contacts 38a.

The actuator 52a comprises an elongated hollow tubular member having aclosed end portion 54a. Extending longitudinally therefrom are foursegmental spring members 56a separated from one another by gaps (notshown). Each of the segmental spring members 56a is tapered in oppositedirections to form oblique surfaces 58a around the center line of theactuator 52a. The oblique surfaces terminate at an annular apex 60a fromwhich the members 56a converge toward the center line of the actuator52a to form guide surfaces 62a. The segmental spring members 56a whenfully compressed have a diameter at the apex 60a less than the internaldiameter of the aperture 46a of the floating contact 44a for a purposeto be set forth more fully hereinafter.

The actuator 52 is secured by any suitable means such as a pin or asshown in the drawing by an epoxy adhesive material to the interior bore62a of a closed plunger 64a. It will be seen by referring to the drawingthat the plunger is shaped so as to allow it to be grasped and pulled aswell as depressed.

In operation the modified form of the invention operates similarly tothe basic form in that the plunger 64a upon being depressed causes theleading surfaces 62a to align themselves with the aperture 46a of thefloating contact 44a. The leading surfaces 62a upon entering theaperture 46a cause the segmental spring members to constrict inwardlytoward the center line of the actuator allowing the leading surfaces 62ato enter the aperture until the apex 60a traverses the aperture andcauses the floating contact to snap thereby breaking the electricconnection between the stationary contacts 38a. The reverse operation,i.e., by pulling on the plunger 64a causes the oblique surfaces 58a toenter the aperture, thereby constricting the segmental members until thediameter of the apex is less than that of the aperture when the floatingcontact snaps downwardly into contact with the stationary contactmembers.

While there have been described herein what are at present consideredpreferred embodiments of the invention, it will be obvious to thoseskilled in the art that modification and changes may be made thereinwithout departing from the essence of the invention. It is therefore tobe understood that the exemplary embodiments are illustrative and notrestrictive of the invention the scope of which is defined in theappended claims, and that all modifications that come within the meaningand range of equivalency of the claims are intended to be includedtherein.

We claim:

1. An electric switch comprising a housing having an axially moveableplunger at one end, a plurality of fixed contact members positionedwithin said housing having their contact surfaces in spaced relation toeach other, an actuator having an end portion disposed within saidplunger with a plurality greater than two of downwardly and divergingaxially extending segmental spring mem- 5 6 bers, said spring membershaving oblique surfaces ex- References Cited tending away from thecenter line of said actuator and UNITED STATES PATENTS leading surfacesextending in the direction of said center line, the junction of saidoblique surfaces and said lead- 2,466,970 4/1949 Schenman 2GO77 ingsurfaces defining a limit of camming action in one 5 21777911 1/1957 P200-77 direction, a return rod biased in the direction of said 3,187,1331/1965 Place 20077 plunger by spring means and positioned within andextending axially and into abutting relation with a closed FOREIGNPATENTS end of said actuator, an axially moveable contact mem- 427,8654/1926 yber positioned in axial relation to said fixed contact mem- 1Obers, said actuator moveable in response to plunger pres- ROBERTSCHAEFER P'lmary Examme' sure to axially cam said moveable contactmember. D. SMITH, In, Assistant Examimer.

